Oekaki Drawing's Layers Flattened

[Frightful]

I just drew a drawing that took forever, and after I posted it I realized a mistake. I tried to edit it to find that it was flattened into one layer. I don't remember flattening the layers, and if I did I believe it says "Are you sure you want to flatten?". Can this be fixed? I've seen a topic where an editable was flattened and Nick fixed it.
Thanks!